Skin Flashcards
(45 cards)
What type of epithelia is found in the epidermis?
Stratified squamous keratinized epithelium
How does thick skin differ from thin skin?
- Thicker epidermal layer
- Found only on the soles of feet and palms of hands
- Hairless
- Has merocrine sweat glands
- Has a 5th layer called the stratum lucidum, a thin, translucent layer
What are keratinocytes?
- Predominant cell type in the epidermis
- Arise from the s. basale and migrate towards the surface
- Undergo keratinization
How is cellular turnover affected in psoriasis?
Can be as rapid as 1 week due to accelerated keratinocyte cell cycling, leading to thockening of the epidermis and accelrated keratinization and desquamation.
What are warts?
Benign epithelial growths caused by papilloma viral infection of keratinocytes
What type of cancer affects the s. basale layer?
Basal cell carcinomas - most common skin cancer
What type of cancer arises from the s. spinosum layer?
Squamous cell carcinomas - 2nd most common
In the s. spinosum, keratinocytes begin to produce ____ ____ on their free ribosomes, which consist of ____ ____ ____. Membrane-bound ____ ____ containing pro-barrier lipids begin to form on the RER.
Keratohyalin granules; intermediate filament-associated proteins; lamellar granules
Cells in the ____ layer first begin to undergo keratinization.
S. Granulosum
The epidermal water barrier is formed when ____ ____ release their lipid contents via exocytosis into the intercellular space.
Lamellar granules
Keratinized cells are shed or “desquamated” from the s.corneum when ____ degrade.
Desmosomes
What are Merkel cells?
- Mechanosensitive touch receptors in the s. basale
- Basal surface of cell associates with afferent nerve ending from the dermis
- Release neuroactive chemicals that stimulate afferent nerve endings
- Most abundant in fingertips
What are Langherhan’s cells?
- Also called dendritic cells
- Found in s. spinosum
- Are the immune cells/APCs of the skin; derived from monocyte-macrophage lineage
What are melanocytes?
- Found in s. basale
- Produce melanin in membrane-bound melanosomes
- Donate melanosomes to keratinocytes for protection against UV radiation
- More melanocytes in areas exposed to the sun
How does melanin provide protection?
Takes a supranuclear position in the cell so that pigment shields the nuclei of keratinocytes from UV radiation
What is malignant melanoma?
- Rare but most dangerous form of skin cancer
- Invades the underlying dermis, and metastasizes by lymph and blood
True or False:
The ratio of melanocytes : keratinocytes varies between races.
False - the activity varies between races
What are three examples of adaptive changes to melanocyte activity?
- Genetically determined forms of melanin (pheomelanin vs eumelanin)
- Rate of melanin production - higher in darker-skinned people
- Rate of lysosomal degradation of melanin - slower in darker-skinned people
____ ____ decreases with age, resulting in paler skin and hair.
Melanocyte population
____ results from autoimmune destruction of melanocytes in symmettrical patches.
Vitiligo
What features increase the surface area between the epidermis and the dermis?
Epidermal ridges and dermal papillae
What creates fingerprints?
- Dermal ridges
- Only present in thick skin
The greater the surface area of the dermal-epidermal interface, the greater the…
Three things
- # of hemidesmosomes (ie. adhesion b/w epidermis and BM to resist friction)
- Gas, nutrient, and metabolite exchange b/w avascular epidermis and dermis
- Population of dividing cells in the germinal layer, and thus the # of keratinocytes being produced
All of these are important in thick skin
What are the two layers of the dermis?
- Papillary layer - consists of loose areolar CT, more cellular, richly vascularized, rich in collagen type I and III
- Reticular layer - consists of dense irregular CT; thicker, less cellular, rich in collagen type I
